Disposable cassette systems are widely used, particularly in medical applications involving the handling of fluids that interact with biological systems. Examples are to be found in U.S. Pat. Nos. 4,493,695, 4,627,833, and 4,713,051.
Where blood is the fluid being transferred, the dangers of contamination are high, and consequently it is generally preferred to utilize disposable tubing and fluid transfer systems rather than attempt to sterilize part or all of the fluid handling system for each use. Incorporation of the essential elements in a relatively low cost cassette minimizes removal and handling time and the dangers of an incorrect setup. The same is true in fluid interchange systems used for ophthalmic surgical applications, such as irrigation and aspiration systems of the type sold by Site Microsurgical Systems, Inc., a Johnson & Johnson subsidiary, under their Model No. TXR, and by CooperVision, Inc., now Alcon, under the Model 10,000. The Alcon Model 10,000 is essentially described in U.S. Pat. No. 4,713,051 to Steppe, et al., and represents a cassette adaptation of an earlier Model 8000 that employed loose tubing sets with peristaltic pumps and passed waste matter to a plastic bag. The Site cassette, as evidenced by U.S. Pat. No. 4,627,833 to Cook, disposes flexible irrigation and aspiration tubings in a rectangular housing having an attached rigid collection vessel through which a reciprocating pump draws a vacuum. In both systems internal flexible lines are juxtaposed so that after the cassette is inserted, line flow can be stopped by clamp actuators in the console which pinch exposed portions of flexible lines against internal surfaces. In operation of both systems, sterile irrigation fluid from a source is fed by gravity to the operative site, and aspirated fluid is pumped from the operative site back to a collection unit.
The Alcon cassette is configured in a known fashion so as to provide a semicircular boss against which the rollers of the peristaltic pump press the irrigation line to force aspiration fluid along.
In the parent U.S. Pat. No. 4,963,131, entitled DISPOSABLE CASSETTE FOR OPHTHALMIC SURGERY APPLICATIONS, issued May 4, 1990, it is shown that the use of internal sliders within a cassette body to transfer force from an external clamp actuator internally into a selected location or locations within the cassette has a number of particular advantages. By confining the area of repeated flexure of the transfer lines to well within the body of the cassette, the danger of contamination of sterile flows from the occurrence of cracks or pinholes in the line due to repeated flexure is greatly minimized. Also, the line geometries within the cassette are straightened, shortened and simplified by virtue of the degrees of design freedom that are available.
In the other parent application to the instant application, Ser. No. 07/596,219, now U.S. Pat. No. 5,163,900 it is shown that the use of separate, interacting cooperative units and the segregation of the supply or irrigation function from the aspiration, pumping and control functions provides substantial advantages. A receiver structure is inserted in the cassette receiving surface or receptacle of the system and provides a flow path for the pumping and transfer of aspiration fluid from the operative site to a collection receptacle. The geometry is also arranged such that the receiver defines an open sided interior volume within which a smaller second disposable unit can be inserted. The smaller disposable unit includes fittings for lines connecting a sterile fluid source to the operative site. The combination of receiver and cassette includes those fittings and internal tubing needed for connection of the aspiration lines to a vent or other form of vacuum control on the system console. Internal sliders in the receiver act upon lines in the disposable cassette to simplify and shorten the internal tubing geometry and provide contamination safeguards. Thus a disposable conduit system is provided that connects the aspiration flow path from the handpiece to the waste collection unit, while sterile fluid pathways are incorporated in a smaller disposable cassette. Prior to the introduction of this concept, cassettes for surgical tubing systems were based on the premise that all operative tubing and other parts must be located within a housing so that by virtue of this prepackaging of the entire unit only external connections need be made.
The cost of disposable cassettes is, however, an item of constant concern as health care expenses continue to mount. Further decreases in the cost of disposable units, without sacrifice of sterility or operative advantages are much to be desired. Improvements in the ease of and safety of handling and installation are also to be incorporated wherever possible. Fundamental reorganization of functions and relationships in an interconnect and control system that extends the features disclosed in the parent application shows how these results can be obtained.